Rolling mill for producing thin strip stock

ABSTRACT

Rolling mill for producing thin strip stock which comprises: a first tension unit acting as a retaining unit, a second tension unit acting as a driving unit, said first and second units comprising each a number of rolls driven at a same peripheral velocity from driving means, said strip to be rolled being passed over said rolls; coupling means arranged between said first and second units and adapted to impart a constant and possibly adjustable value to the ratio of the tangential speeds of said rolls of said first and second units, means for driving with an adjustable torque the combined mechanism consisting of said first and second tension units, and a four-high stand disposed between said units and provided with work rolls of relatively small diameter rotatably driven by frictional engagement from positively driven supporting rolls.

United States Patent [72] Inventor Pierre Gay La Tour en Jarez, France [21 Appl. No. 799,228 [22] Filed Feb. 14, 1969 [45] Patented May 25, 1971 [73] Assignee Compagnie Des Ateliers Et Forges De La Loire (St. Chamond, Firminy, St. Etienne, Jacob-Holtzer) Paris, France [32] Priority Feb. 16, 1968 [33] France [31] 1218176 [54] ROLLING MILL FOR PRODUCING THIN STRIP STOCK l 1 Claims, 4 Drawing Figs.

[52] U.S. C1 72/205,

72/238, 72/249 [51] Int. Cl B21b 39/08, B21b 3 5/00 [50] Field of Search 29/17, 18; 72/205, 226, 249

[56] References Cited UNITED STATES PATENTS 1,881,056 10/1932 Bain 72/205X 2,118,560 5/1938 Hudson 72/205 2,287,380 6/1942 Klein et a1. 72/205 3,098,403 7/1963 Metzger 72/249X 3,394,574 7/1968 Franck et al 72/205 FOREIGN PATENTS 212,206 4/1967 Sweden 72/205 Primary Examiner-Milton S. Mehr AttorneyWenderoth, Lind and Ponack ABSTRACT: Rolling mill for producing thin strip stock which comprises: a first tension unit acting as a retaining unit, a second tension unit acting as a driving unit, said first and second units comprising each a number of rolls driven at a same peripheral velocity from driving means, said strip to be rolled being passed over said rolls; coupling means arranged between said first and second units and adapted to impart a constant and possibly adjustable value to the ratio of the tangential speeds of said rolls of said first and second units, means for driving with an adjustable torque the combined mechanism consisting of said first and second tension units, and a four-high stand disposed between said units and provided with work rolls of relatively small diameter rotatably driven by frictional engagement from positively driven supporting rolls.

Patented May 25, 1971 3,580,033

F @5 J L: 1 g (QES J PIERRE GAY, Inventor YIIDAJJAJQMXJLL ttttttt ys Patented May 25, 1971 3,580,033

4 Sheets-Sheet 2 PIERRE GAY, Inventor Bmwmimawlp Attorneys Patented May 25, 1971 4 Sheets-Sheet 4 PIERRE GAY, gnventor y, MwluM/xLd/i Attorneys ROLLING MILL FOR PRODUCING THIN STRIP STOCK The present invention relates to improvements in or relating to rolling mills for producing relatively thin metal strips.

The present trend, notably in the steel industry is to produce increasingly thinner steel strips by rolling. Thus, in contrast to the hitherto current tendency to attenuate the thickness of tin plate strips not beyond 0.0085, is now desired to produce socalled double reduction tin plates having a thickness of the order of 0.006 inches.

At present this double reduction is obtained by rolling mill personnel operating the same equipment, i.e. the same rolling mills as before.

Obviously this procedure cannot be regarded as technically satisfactory or economical. In fact, on the one hand conventional rolling mills can hardly make products having an adequate flatness and on the other hand this double-reduction operation involves relatively prolonged additional operation of the rolling mill equipment, for the thinner the desired product, the lower the production rate expressed in tons per hour.

It is the essential object of this invention to provide a rolling mill characterized essentially in that it is free of the above mentioned inconveniences; to this end, the improved rolling mill according to this invention comprises the following two principal features:

1. It is designed for insertion in a line along which the strip travels continuously but without interfering with the operation of this line. The double-reduction operation can thus take place concomitantly with the other operations performed along said line. Thus, for example, if the desired product is a double-reduction tin plate adapted to be tinned in the cold-rolled state, the tinning line will comprise in succession the double-reduction rolling mill, a scouring equipment and eventually the tinning equipment proper.

2. The double-reduction can be performed to the requisite standards while obtaining and end product having very close thickness tolerances and a satisfactory flatness.

A rolling mill according to this invention comprises in combination a first tensioning or retaining unit, a second tensioning or driving unit, each unit comprising a number of rolls driven at a same peripheral speed by adequate driving means, the strip to be rolled passing over said rolls; coupling means disposed between said two units and adapted to impart a constant, possibly adjustable, value to the tangential speed ratio of the rolls of said two units and a four-high stand disposed between said two units and provided with working rolls of relatively small diameter which are rotatably driven by frictional contact from driven supporting rolls.

According to a first feature characterizing this invention the four-high stand supporting rolls are driven at a given, possibly adjustable speed and the mechanism consisting of said pair of tensioning units is driven under adjustable-torgue conditions.

According to this invention, hydraulic cylinder and piston units are used for providing the clamping force of said fourhigh stand.

Still according to this invention, the means for driving said tensioning units comprise first gear means adapted to synchronize the movements of rotation of the rolls of said retaining unit; second gear means similar to said first gear means for synchronizing the movements of rotation of the rolls of said driving unit; a driving shaft for each one of said units; a coupling gear mechanism disposed between said driving shafts for providing a fixed or possibly adjustable gear ratio between the rotational speeds of said and a coupling gear mechanism driving shaft to which an adjustable torque is applied.

According to a specific feature of the above-described means, a variable-speed reduction gearing is so associated with said coupling gear mechanism that the ratio of the rotational speeds of said unit driving shafts can be adjusted at will.

According to this invention, the adjustable torque applied to said coupling gear mechanism driving shaft is produced by a motor.

According to a modified form of embodiment of this invention, said coupling gear mechanism driving shaft is driven in turn through a clutch adapted to slip when a predetermined and adjustable torque valve is attained, said clutch being driven in turn from a constant-speed motor.

The rolling mill according to this invention may advantageously comprise two identical four-high stands disposed tandem wise between said tensioning units and adapted to be operated by turns.

Other features and advantages characterizing the invention will appear as the following description proceeds with reference to the annexed drawings illustrating diagrammatically by way of example a typical form of embodiment of the invention which is given for the sake if illustration, it being understood that various modifications and changes may be brought to the practical embodiment of the means illustrated therein without departing from the spirit and scope of the invention as set forth in the appended'claims. In the drawings:

FIG. 1 illustrates in diagrammatical side-elevational view a typical construction of the rolling mill according to this inven tion;

FIG. 2 is a diagram illustrating the forces to which the working rolls of a four-high stand are submitted, assuming that the supporting rolls of this stand are positively driven as in the rolling mill of this invention;

FIG. 3 illustrates diagrammatically a typical form of embodiment of the driving means contemplated for rolling mill according to this invention; and

FIG. 4 is a detailed view of the arrangement of FIG. 3.

Referring to the drawings and notably to FIG. 1, it will be seen that the rolling mill according to this invention comprises one or two high stands disposed between two units adapted to continuously tension the metal strip to be thin-rolled.

The retaining unit I disposed at the inlet end of the device (it is assumed that the strip 5 travels in the direction of the arrow f) comprises five rolls 2 and the driving unit 3 disposed at the outlet end also comprises five rolls 4. The strip 5 is passed in succession over rolls 2, then over rolls 4, as shown in the drawings. 0

The rolls 2 of unit 1 are operatively and mechanically interconnected so that they revolve at a substantially uniform peripheral speed. The rolls 4 of unit 3 are interconnected in the same fashion.

Mechanical gear transmission means are provided between the retaining unit 1 and the driving unit 3 so that the ratio of the peripheral speed of the rolls of unit 1 to the peripheral speed of the rolls of unit 3 be constant throughout the operation of the device. Under these conditions, the action of the units 1 and 3 causes the strip 5 to be elongated.

A presser roller 6 is provided at the inlet end of the retaining unit I and a similar presser roller 7 is also provided at the outlet of the driving unit 3 so that the strip 5 will remain unstressed upstream of unit 1 and downstream of unit 3.

A rolling stand 8 is disposed between said units 1 and 3. In

the specific form of embodiment illustrated in the drawingsv this rolling stand consists of two tandem-arranged identical four-high stands. However, only one of these four-high stands is operated, the presence of two paired stands enabling the replacement of worn work rolls of one stand during the operation of the other stand, so that the operation may proceed as continuously as possible.

Each four-high stand comprises tow work rolls 9. The diameter of these work rolls is relatively small in order to facilitate the rolling of thin products; therefore, these rolls are not positively driven. Each work roll is therefore equipped with driven supporting rolls 10 so as to be driven therefrom by frictional contact therewith.

In this specific form of embodiment the clamping system consists of hydraulic cylinder and piston units 1 1.

It will be noted that the above-described arrangement is advantageous not only on account of the possibility of inserting it in to a rolling line but also in that it is capable of rolling products while adhering to very close thickness tolerances.

The strip exerts on the work rolls 9 a vertical reaction R- (the clamping effort). This reaction R is not coplanar to the axes a rolls 9 and creates a reaction torque cancelled by the friction forces F developing between the supporting and work rolls and also by.the retaining forces Fr and traction forces Ft exerted by the strip. This assembly of horizontal forces F, Fr and Ft has a horizontal resultant T exerted against the axis of work rolls 9. This reaction T causes the work roll 9 to yield in the horizontal plane (inasmuch as small-diameter work rolls are used).

The consequence of this yielding movement on the strip flatness is the same as the presence of a barrel-shaped surface on rolls 9 (shape variation about the cylindrical shape). Therefore, since it is known that the variation in the convexity of the cylinders or rolls will modify the flatness of the rolled products, it will be possible to modify this flatness by altering the horizontal resultant T.

However, this variation of T cannot be utilized for practical purposes, i.e. correcting the lack of flatness, unless the rolling mill has particular characteristics.

In fact, considering the product to be rolled, the rolling mill, the lubricating conditions, the rolling speed, it is clear that T further depends on the tensions Fr and Ft and also on the clamping force R. Under these conditions it will be extremely difficult to find a suitable adjustment or setting combining the proper flatness with the desired thickness of the strip product.

in the foregoing it has already been explained that the rolling mill according to this invention has hydraulic clamping means; therefore, the clamping efiort R can be adjusted to the desired value, the variations in the other parameters leaving R unchanged. (This would not be obtainable with mechanical clamping means). Besides, in this rolling mill the elongation is preset or imposed, so that the desired reduction will be obtained.

lt can thus be shown that the resultant T depends only on the driving torque applied to the tension units. This can easily be detennined by means of conventional formulae utilized for recalculating the efforts developing during the rolling operation, or more directly, considering for example that this resultant T depending on Fr, Fr and R will be determined if R is given and the other two factors (i.e. the reduction value and the driving torque exerted on the pair of tension units 1 and 2) are imposed.

Now the rolling mill according to this invention is characterized in that it is so driven that the supporting rolls are driven at a given, possibly adjustable speed, and that the.

mechanism constituting said tension units is driven under adjustable torque conditions.

Considering the data set forth hereinabove, it will only be necessary to vary the driving torque of the tension units for varying the above-defined resultant T and therefore correct the insufficient flatness of the strip.

FIG. 3 illustrates by way of example a kinematic chain of the drive between a motor and the tension units 1 and 2 of a rolling mill according to this invention.

The shaft of each roll 2 has wedged or keyed thereon a pinion such as 12. This set of gears 12 will synchronize the rotational movements of rolls 2. A similar set of gears 13 is provided for synchronizing the rotational movements of rolls 4.

A drive shaft emerges from each tension unit 1 and 2, as shown at 14 and 15 respectively. These drive shafts 14 and 15 are drivingly interconnected by a coupling gear mechanism 16 providing a fixed gear ratio between the rotational speeds of shafts 14 and 15.

It will be noted that it would not constitute a departure from the basic principle of this invention to associate with this coupling gear mechanism a variable-speed gearing 20 permitting the adjustment of the speed ratio between shafts l4 and 15. v

The coupling gear mechanism 16 comprises a driving shaft 17 receiving an adjustable torque. The motor producing this torque is shown by way of example at 18 in the drawings, but it would not constitute a departure from the spirit of the invention to substitute a clutch for this motor, this clutch being adapted to slip when a predetermined torque value is attained, and being driven from a constant-speed motor.

The rolls 10 supporting the work rolls 9 drive these work rolls by frictional contact. To this end a drive motor 22 (FIG. 4) rotatably driving a shaft 24 may be provided. This shaft 24 transmits the drive to a gearing 26 driving in turn the shafts 28 of rolls 10.

Of course, the specific forms of embodiment illustrated and described herein should not be construed as limiting the scope of the invention since various modifications may be brought thereto without departing from the spirit and scope of the invention as set forth in the appended claims.

lclaim:

1. A rolling mill for producing a relatively thin metal strip comprising driving means, a first tension unit acting as a retaining unit, a second tension unit acting as a driving unit, said first and second units comprising each a number of rolls driven at the same peripheral velocity from said driving means, means for passing said strip to be rolled over said rolls, coupling means interconnecting said first and second units to provide a predetermined valve to the ratio of the tangential speeds of said rollsof said first and second units, means for driving with predetermined torque and combined mechanism consisting of said first and second tension units, and a fourhigh stand disposed between said units comprising positively driven supporting rolls and work rolls of relatively small diameter rotatably driven by frictional engagement from said supporting rolls.

2. A rollingmill as set forth in claim 1, including means for varying the speed of rotation of said supporting rolls.

3. A rolling mill as set forth in claim 2, wherein said four high stand comprises hydraulic cylinder an piston units for urging said rolls together.

4. A rolling mill as set forth in claim 3, wherein said means for driving the combined mechanism comprising said first and second tension units comprise gear means to synchronize the rotational movements of the rolls of said retainingunit, gear means to synchronize the rotational movements of the rolls of said driving unit, a drive shaft for each one of said units, a gear mechanism arranged between said drive shafts for imparting a speed ratio between the rotational speeds of said shafts, and a shaft for driving said gear mechanism under predetermine torque conditions.

5. A rolling mill as set forth in claim 4, including means adjusting the ratio of the rotational speeds of the rolls of said units.

6. A rolling mill as set forth in claim 5, wherein said means for adjusting the ratio between the rotational speeds of the rolls of said units are a variable-speed reduction gearing.

7. A rolling mill as set forth in claim 4, wherein the means arranged to apply a predetermined torque to said gear mechanism driving shaft are a constant torque motor.

8. A rolling mill as set forth in claim 4, in which the means arranged to apply a predetermined torque is a clutch arranged to slip when a predetermined adjustably torque is attained, said clutch being driven from a constant-speed motor.

9. A rolling mill as set forth in claim 4, wherein the means arranged to apply a predetermined torque are adjustable to select the torque.

11. A rolling mill as set forth in claim 1, wherein another four-high stand is disposed tandemwise with said four-high stand to permit the alternate operation of one or the other stand as required for maintenance and repair purposes. 

1. A rolling mill for producing a relatively thin metal strip comprising driving means, a first tension unit acting as a retaining unit, a second tension unit acting as a driving unit, said first and second units comprising each a number of rolls driven at the same peripheral velocity from said driving means, means for passing said strip to be rolled over said rolls, coupling means interconnecting said first and second units to provide a predetermined valve to the ratio of the tangential speeds of said rolls of said first and second units, means for driving with predetermined torque and combined mechanIsm consisting of said first and second tension units, and a fourhigh stand disposed between said units comprising positively driven supporting rolls and work rolls of relatively small diameter rotatably driven by frictional engagement from said supporting rolls.
 2. A rolling mill as set forth in claim 1, including means for varying the speed of rotation of said supporting rolls.
 3. A rolling mill as set forth in claim 2, wherein said four high stand comprises hydraulic cylinder an piston units for urging said rolls together.
 4. A rolling mill as set forth in claim 3, wherein said means for driving the combined mechanism comprising said first and second tension units comprise gear means to synchronize the rotational movements of the rolls of said retaining unit, gear means to synchronize the rotational movements of the rolls of said driving unit, a drive shaft for each one of said units, a gear mechanism arranged between said drive shafts for imparting a speed ratio between the rotational speeds of said shafts, and a shaft for driving said gear mechanism under predetermined torque conditions.
 5. A rolling mill as set forth in claim 4, including means adjusting the ratio of the rotational speeds of the rolls of said units.
 6. A rolling mill as set forth in claim 5, wherein said means for adjusting the ratio between the rotational speeds of the rolls of said units are a variable-speed reduction gearing.
 7. A rolling mill as set forth in claim 4, wherein the means arranged to apply a predetermined torque to said gear mechanism driving shaft are a constant torque motor.
 8. A rolling mill as set forth in claim 4, in which the means arranged to apply a predetermined torque is a clutch arranged to slip when a predetermined adjustably torque is attained, said clutch being driven from a constant-speed motor.
 9. A rolling mill as set forth in claim 4, wherein the means arranged to apply a predetermined torque are adjustable to select the torque.
 10. A rolling mill as set forth in claim 4, wherein a presser roller is provided at the inlet end of said retaining unit and another presser roller is provided at the outlet end of said driving unit, whereby the strip can remain unstressed upstream and downstream of the rolling mill.
 11. A rolling mill as set forth in claim 1, wherein another four-high stand is disposed tandemwise with said four-high stand to permit the alternate operation of one or the other stand as required for maintenance and repair purposes. 